Carboplatin is a drug that is used as a chemotherapy treatment for cancer. Measurement of carboplatin by HPLC/UV methods is insensitive due to the lack of significant UV absorption. Although derivitization of carboplatin has been used, these methods only produced limits of quantitation near 0.13 µM and required run times of >25 minutes per sample. Other HPLC/MS methods required extensive clean-up of the biological samples. In addition, the HPLC/MS methods suffered from assay interferences due to lack of retention of the polar carboplatin on the reversed phase column. Here we report on the development of a precipitation method with a polar HPLC column (HILIC) for the sensitive HPLC/MS/MS quantitative analysis of carboplatin from plasma.